A 35-year-old male patient presents with headache and dizziness for 6 months, worsening over the past week accompanied by blurred vision, nausea, vomiting, and poor appetite. BP: 190/105 mmHg, Hb: 69 g/L, urinary protein (++), urine sediment examination shows 3-5 RBCs/HPF, serum creatinine: 806 μmol/L, BUN: 33 mmol/L, Ccr: 9 ml/min, CO₂CP: 14 mmol/L. Ultrasound reveals bilateral kidney sizes: left kidney 9.1×4.8×14.0 cm, right kidney 8.9×4.5×3.8 cm. The most likely diagnosis is: